Polyester yarn production

ABSTRACT

A method and apparatus are disclosed for the production of a novel industrial polyester filament yarn of improved uniformity wherein a plurality of filaments are melt-spun into a heated zone coupled with controlled cooling. The yarn produced has improved long and short term Uster uniformity and improved uniformity of physical properties, particularly breaking strength, as shown by a reduced standard deviation of breaking strength. The yarn is produced by melt spinning into a heated zone which maintains the filaments molten for intervals below the spinneret face and subsequently quenching the filaments with a radial outflow of cooling gases, thereby producing a low birefringence yarn which is capable of being drawn at high draw ratios to high tenacities.

States Patent Stefan Jan. 7, 1975 POLYESTER YARN PRODUCTION [75]Inventor: Richard H. Stofan, Shelby, NC. [73] Assignee: FiberIndustries, Inc., Charlotte,

[22] Filed: July 6, 1971 [21] Appl. No.: 160,019

[52] US. Cl 57/140 R [51] Int. Cl D02g 3/22 [58] Field of Search 57/140R [56] References Cited UNITED STATES PATENTS 3,342,027 9/1967 Mehler57/140 R 3,365,875 1/1968 Hall 57/140 BY X 3,419,060 12/1968 Goy et al.57/140 R X 3,664,114 5/1972 Ammons et al 57/140 R 3,670,489 6/1972Jackson et al. 57/140 R Primary Examiner-Donald E. Watkins Attorney,Agent, or Firm-Herbert M. Adrian, Jr.

[57] ABSTRACT A method and apparatus are disclosed for the production ofa novel industrial polyester filament yarn of improved uniformitywherein a plurality of filaments are melt-spun into a heated zonecoupled with controlled cooling. The yarn produced has improved long andshort term Uster uniformity and improved uniformity of physicalproperties, particularly breaking strength, as shown by a reducedstandard deviation of breaking strength. The yarn is produced by meltspinning into a heated zone which maintains the filaments molten forintervals below the spinneret face and subsequently quenching thefilaments with a radial outflow of cooling gases, thereby producing alow birefringence yarn which is capable of being drawn at high drawratios to high tenacities.

4 Claims, 3 Drawing Figures AIR SUPPLY DRAWING STAGE TAKE UP ON PACKAGEPatented Jan. 7, 1975 3,858,386

5 Sheets-Sheet 1 DRAWING I STAGE TAKE UP ON PACKAGE F G. INVENTOR.

RICHARD H. STOFAN Patented Jan. 7, 1975 3,858,386

3 Sheets-Sheet 2 (INERT) I/2 TE 29....

I I I I I I 6 v8 IO I2 I4 I6 DISTANCE IIN.) FROM PACK FACE TO TOP OFSINTERED METAL TUBE I INVENTOR FIG 2 RICHARD H.. STOFAN ATTORNEYPatented Jan. 7, 1975 3,858,386

3 Sheets-Sheet 3 Ten (gpd) I 2O 3O 4O 5O 60 AIR FLOW (SCFM) F I G. 3INVENTOR RICHARD H. STOFAN ATTORNEY POLYESTER YARN PRODUCTION BACKGROUNDOF THE INVENTION In the production of polyester industrial yarn, oftenreferred to as heavy denier continuous filament yarn, it has often beenthe practice to produce undrawn filaments of low birefringence such thathigh draw ratios can subsequently be utilized, thereby obtaining thehighest degree of molecular orientation and consequently hightenacities. Such high orientation contributes to the high tenacity ofthe resulting fibers. It was previously discovered that polyester fibersof low birefringence can be most highly oriented in subsequent drawingsteps, but that as filament spinning speeds increase, birefringencetended to increase because of the induced orientation of the filamentwhich occurs in the rapid takeup of the yarn. This results in increasedpulling tensions on the yarn in the spinning column, i.e., increases incolumn draw down. To alleviate the draw down in the column, variousprocedures have been incorporated into the spinning, including higherextrusion pressures and means for maintaining the filaments molten for aperiod of time after extrusion. The filaments on quenching and drawing,while achieving high tenacities and modulus and desirable elongations,are found to be deficient in uniformity as measured in percent Uster.This results in a higher standard deviation for the physical properties,such as breaking strength, which is of most critical importance toindustrial yarn.

It is therefore an object of the present invention to describe a methodfor producing a heavy denier industrial polyester yarn of improveduniformity of physical properties.

It is another object of the present invention to pro vide apparatus forspinning such polyester filament yarns.

It is another object of the present invention to provide a heavy denierindustrial polyester filament yarn of high tenacity, improved long andshort term percent Uster values and lower standard deviation in breakingstrength.

These and other objects will become apparent to those skilled in the artfrom a description of the invention which follows.

DESCRIPTION OF THE INVENTION In accordance with the invention, a methodis provided for producing an industrial polyester filament yam ofimproved uniformity comprising melt spinning a plurality of filaments atan extrusion temperature above the polymer melting point into a heatedzone maintained at a temperature of 260 460 centigrade, maintaining saidfilaments in said heated zone for filament travel distance of about 6 to24 inches and hence, immediately passing said filaments about a gaseousquenching zone, directing quenching gases onto said filaments in aradial outward flow direction, said quenching gas being maintained at atemperature of about to 50 centigrade in a gaseous volume of about to130 standard cubic feet per minute to provide a controlled cooling ofsaid filaments and taking said filaments up as a yarn of improved Usteruniformity.

The heavy denier industrial polyester filament yarn produced inaccordance with this invention has a denier per filament of 3 to 20, atenacity of more than 7.0

grams per denier, a long and short term percent Uster of less than 1.5,and more preferably a long term percent Uster of less than 1.0, atensile factor (TE of more than 28 and a breaking strength standarddeviation of less than 0.20 grams per denier as measured in yarns acrossa beam.

The improved uniformity of the yarn is achieved primarily through theutilization of controlled temperature conditions from immediatelyadjacent to the extrusion point to the cooling of the filaments to atemperature below their second order transition temperature. Theimprovement is not only highly pronounced in Uster uniformity, but alsoin reduction in the average standard deviation of physical properties,particularly tensile strength. It is also noticeable in the reduction ofboth major and minor beaming defects as noted by Lindley defect countingat beaming.

DETAILS OF THE INVENTION The invention will be more fully described byreference to the drawings wherein:

FIG. 1 is a front elevational and partial schematic of the apparatus ofthe present invention showing more particularly the relationship of theextrusion heated zone and quenching apparatus in a spinning column;

FIG. 2 is a graph which illustrates the relationship between thequenching distance from the spinneret face as it relates to long termUster values and tensile factor (re FIG. 3 is a graph which relates longterm Uster, elongation, tensile factor (TE) and tenacity with variousquench gas flow rates.

Referring more particularly to FIG. 1, the schematic drawing of spinningpack 10 is representative of a standard polyester pack which includesfinal filtration means for the polymer and a spinneret with apreselected number of holes for the extrusion of polymer. The polymerconveyed to the pack is maintained at a spinning temperature which isnormally comfortably above the melting temperature of the polymer, i.e.,about 257 centigrade for polyethylene terephthalate. Thus, spinningtemperatures are normally in the range of about 290 to 310 centigrade.The spinneret utilized is selected in accordance with the denier andfilament count of the yarn being produced. If desired, one or more yarnscan be spun from a single pack in a single column as illustrated in thedrawing.

The spinning speed varies with the particular process and fiber typebeing spun, but generally is in the range of 2,000 to 10,000 feet perminute or more at wind up in a spin-draw process.

The molten polymer, as it is extruded from pack I0, immediately enters aheated zone which is maintained at an elevated temperature by a heatedcylindrical shroud 12 which preferably is positioned adjacent to pack 10and extends downwardly into the spinning column for a distance of about6 to 2-4 inches. The shroud has an internal diameter of sufficient sizeto permit safe passage of the filaments therethrough without danger ofcontact with the heated shroud. Conveniently, leeway of one to severalinches of distance is provided between the outside filament travel lineand the inside diameter of the shroud. The shroud. is heated preferablyby internal heating means such as electrical resisters, circulatingfluids or the like conventional heating means to produce an internalsurface temperature on the shroud in the range of 260 to 460 centigrade,and

more preferably 300 to 360 Centigrade. Such shroud temperatures providea heated zone of temperatures slightly less than the surfacetemperature, but because of heat radiated from the spinning pack andmolten extrudate, a temperature near that of the shroud is readilymaintained. The exact temperature utilized is primarily dependent uponthe size of the shroud, distance away from the filaments, heat loss fromthe shroud area, filament denier, polyester type and the likeconsiderations. The temperature selected is one sufficient to maintainthe as-spun polymer in a molten condition as it passes through theshroud area.

Immediately adjacent to the lower section of heated shroud 12 is outflowquench stick l4. Quench stick 14 is centered among the filaments andpositioned by means of positioning guide (piece pin) 16 in a centrallocation under the pack and spinneret. The filaments are guided down thequench stick so as not to come in contact therewith, but to spread thefilaments uniformly around the quench stick. Quench stick 14 ispositioned by means of positioning guide 16 and spacer 18, so as toconveniently position each quench stick in the same location in aplurality of packs and spinning columns.

The quench stick preferably extends into the area of the heated shroudso as to provide a controlled cooling immediately as the filaments exitfrom the shroud. As will be appreciated by those skilled in the art, therapid passage of fibers down the spinning column creates a downwarddraft of convection currents which tends to carry both the heat of theshroud and the cooling effect of the quench gases downwardly along thefilament path of travel. Therefore, by utilizing the preferred quenchstick positioning, the most desirable control of cooling is obtained.

The quench stick is preferably made of a porous material, such asceramic, or sintered metal in a manner which provides a predetermined,even flow of air throughout the length and circumference of the stick.Such quenching sticks are commercially available in a variety ofporosities suitable for this application.

The air flow through the quench stick affects the quality of the yarnproduced and therefore, for a given spinning process a preferred gasflow, e.g., air, results in the most desirable spinning. It has beenfoundthat the air flow as measured in standard cubic feet per minute(SCFM) is proportional to the total denier of the yarn being spun andthe spinning speed with higher total deniers and higher speeds requiringhigher flow rates. For instance, the air flow is in a gas volume ofabout 20 to 130 SCFM with the preferred air flow in the range of about20 to 60 SCFM. This is more clearly illustrated in FIG. 3 which relateschanges in yarn physical properties with changes in air flow rates for a1000/192 industrial yarn. It will be noted from this graph that the bestresults for this yarn at a 5.8 draw ratio is an air flow of about 40SCFM.

Ambient quench gas temperatures have been found to be satisfactory,although in the compression of the gas, a temperature rise is oftenunavoidable. Therefore, under certain climatic conditions, it may bedesirable to cool such gases so as to preferably utilize a quench gastemperature within the range of to 80 centigrade, and more preferablyabout 25 to 50 centigrade.

The quench stick length and diameter are selected in accordance with thespinning speed, filament count,

total denier, air flow desired and the like parameters, so as to providecontrolled cooling of the yarn in the manner described herein. In apreferred embodiment, such quench sticks are normally of a diameter ofabout 1 to 4 inches and a length of about 8 to 20 inches.

Upon quenching the filaments, a spin finish is applied and the filamentsdrawn and taken up on a package as a finished yarn or alternatively,taken upon a package in an undrawn state. In accordance with the presentinvention, it is preferable to split the threadline into two or moreportions and apply the finish separately to each of the portions, suchas by utilizing dual finish rolls 20. It has been found that it isparticularly important to insure that the as-spun filaments do not touchany portion of the spinning column or apparatus until the application ofthe spin finish. Therefore, the split threadline and multiple or dualfinish applicators are particularly important to insure that strayfilaments do not come in contact with items such as the quench or stickor air supply therefor. As is often desired in using a split threadlinequench, the yarns may be retained separately and taken up or drawnseparately. Alternatively, the split threadlines can be recombined atthe drawing stage and taken up as a single yarn;

While it has been described that the yarns may be taken up on a packageafter the application of the spin finish, it is normally most desirablein a modern polyester production plant to immediately thereafter drawthe yarn in one or more stages under known drawing conditions and heatset and/or relax the yarn if desired prior to taking the yarn up as afinished product. In industrial yarns, to which the present invention isprimarily concerned, yarns are normally drawn at the highest achievabledraw ratio which can be successfully processed in continuous operation.Thus, draw ratios in excess of 3, and more preferably on the order of 4to about 6.5 to l are preferably utilized with multi-stage drawing beingthe preferred method of operation. The actual total draw ratio utilizedis dependent upon the as-spun birefringence which, as noted above, ispreferably as low as possible so as to achieve the highest draw ratio.Thus, such drawn yarns have tenacities in excess of 7 grams per denier,and more preferably, in'the range of 8 to l 1 grams or more per denier.

Tensile factor, i.e., TB, is determined by multiplying the tenacity ingrams per denier times the square root of the elongation at break. Theyarns produced in accordance with the present method have tensilefactors greater than 28 and more preferably, greater than 30. Typically,the range of tensile factor is between 28 and 40.

The yarns of the present invention are preferably high tenacityindustrial yarns such as tire yarns, conveyor belt yarns, sewing threadsand the like, having denier per filaments of at least 1.0 and morepreferably 3.0 to 20 or more. Total drawn deniers of such yarns rangefrom about to 10,000 with most yarns having total deniers of about 500to 3,000. All of such yarns are considered to be heavy deniers.

As has been noted above, the long, i.e., inert, and the short, i.e.,normal, percent Uster of yarns produced in accordance with the presentinvention is less than 1.5, and more preferably less than 1.0. The Usteris measured in accordance with Uster Evenness Tester, Model GGPC 10, inaccordance with the manufacturers recommended procedure, with theproviso that a feed tension of 25 grams is utilized on the yarn and ayarn feed rate of 25 yards per minute is fed to the tester for at least3 minutes. The rotofil setting of the tester is placed at number 3 forconventional industrial yarns.

The breaking strength standard deviation (0) of yarns produced inaccordance with the present invention is also substantially improvedover previous industrial yarn processes. Such breaking strength standarddeviation is less than 0.20 grams per denier betweenposition-to-position yarns and most preferably, less than 0.15 grams perdenier, when measured in accordance with ASTM Method D885-68. Thestandard deviation is calculated based upon the testing of at leastsamples of yarn from position-to-position across production machines. Itis often more convenient to measure the standard deviation of the yarnsacross a beam and such yarns fall within the specified range.

With the improved uniformity of the yarns produced in accordance withthe present invention, marked improvement will be noted in major andminor defects in beaming as compared to previously produced yarns.

The preferred polyesters used in this invention are obtained fromterephthalate acid via any of the known polymerization routes, i.e.,ester interchange, direct esterification, BHET and the like, wherein atleast 75 percent of the recurring structural units of the polyester areglycol terephthalate structural units. The polymers used are fiberforming and preferably of an intrinsic viscosity of at least 0.45 up to1.00 or more as measured in 8 percent orthochlorophenyl at 25centigrade.

As conditions for heat setting, a temperature of 120 300 centigrade anda time of 001-2 seconds may be adopted.

While polyester polymer used in the present invention preferablycontains at least 75 mol percent of ethylene terephthalate units and asother acid components when used, a dibasic acid such as phthalic acid,isolphthalic acid, adipic acid, oxalic acid, sebacic acid, suberic acid,glutaric acid, pimelic acid, fumaric acid and succinic acid may be used.A polymerization degree modifier like propionic acid may be used. Asalcohol component, a divalent alcohol such as polymethylene glycolhaving 2-l0 carbon atoms (trimethylene glycol and butylene glycol) andcyclohexane dimethanol may be cited. And they may contain a smallamountof the following compound as a modifier, S-oxydimethyl isophthalate,5-oxydimethyl hexahydroisophthalate, benzene-l,3,5-tricarboxylic acid,para-carbomethoxy phenyl diethyl phosphonate, 3,5-dicarboxy phenyldiethyl phosphonate, pentaerythritol, glycerol, glucose, phosphoricacid, triphenyl phosphate, tri-pcarbomethoxy phenyl phosphate, triphenylphosphinate, triphenyl arsenite, tricapryl borate, sorbitan, trimesicacid, diethylene glycol and the like.

The following examples illustrate certain preferred embodiments of thepresent invention. Unless otherwise indicated, all parts and percentagesused herein are by weight and all temperatures are in degreescentigrade.

EXAMPLE I Polyethylene terephthalate was produced in accordance with acontinuous polymerization process to provide a molten polymer having anintrinsic viscosity of 0.88, as measured in the final product, which wasfed directly to a spinning pack and apparatus in accordance with FIG. 1.The polymer was spun at a spinning temperature of 297 to 300 centigradeat a rate of 30.9

pounds per hour. The yarn spun was 1000/192 yarn utilizing a splitthreadline wherein one-half the filaments were split on either side ofthe quench stick. A spin finish was applied utilizing dual finishapplicator rolls and the yarn recombined for drawing; ina spin-drawprocess. The yarn was drawn to a total draw ratio of 5.8.

During the spinning of the yarn, various parameters with respect to theoutflow quench system and heated shroud were changed to determine theeffect on the yarn properties. In accordance with FIG. 2, the distanceof the initiation of outflow quench from the spinning pack was variedfrom 6 inches to 16 inches, and the effect on tensile factor and percentUster (inert), i.e., long term, was measured. The spinning was carriedout at a set quench air flow of 30 SCFM. The results are graphicallyillustrated in FIG. 2.

The experiments were continued in the same manner with the spinning at arate of 30.9 pounds per hour, the outflow quench distance beingapproximately 10 inches from the spinning pack, quench air temperatureat about 40 centigrade, the pack to outflow spacer distance beingthree-quarters of an inch, and the shroud temperature at 320?centigrade. With these preset conditions, the air flow was varied from20 SCFM to 60 SCFM to determine the effect on percent Uster (inert),tensile factor, i.e., TE percent elongation at break (E), and tenacityin grams per denier (gpd). These effects are shown graphically in FIG.3.

While variations in the noted spinning parameters have the noted effectson the yarn quality and spinning performance, it should be noted thatthis Example illustrated the preferred parameters for 1000/ I92 yarn ina spin-draw process. As will be appreciated by those skilled in the art,changes in the polymer being spun, the particular denier thereof, andthe like, will affect the preferred operating conditions such as byshifting the various curves in the graphs of FIGS. 2-3 to the right orleft as the case may be. Such changes in these spinning parameters toobtain the :most preferred conditions for a given yarn will be readilyascertained from the guidance and exemplification given herein.

EXAMPLE 2 The process of the present invention was compared to standardproduction spinning processes which included the use of a heated shroudat a temperature of 320 centigrade, but without an outflow quench. Thespinning process utilized 0.88 intrinsic viscosity polyethyleneterephthalate, a spinning rate of about 3] pounds per hour, a spin-drawprocedure at a total draw ratio of 6.08 to produce a 1020/ I92 yarn. Thepercent Uster of standard production yarn utilizing the heated shroudwas then compared with the process of the present invention wherein theheated shroud was utilized at the same temperature but combined with theoutflow quench of the air flow of 40 SCFM, a quench air temperature ofabout 40 centigrade, and a quench distance of about 10 inches from thespinning pack. All other conditions were the same as the comparison. Thestandard production yarn had a percent Uster (inert) of 2.3, whereas theyarn of the present invention had a percent Uster (inert) of 0.5.

The breaking load of the yarn of the present invention was 9,072 grams.Standard deviation of breaking load in position-to-position, as measuredin yarns across a beam was 0.15 grams per dlenier. The standardproduction yarn had a breaking load of 9,096 grams,

with a standard deviation in breaking load in positionto-position, asmeasured in yarns across a beam, of 0.21 grams per denier. The number ofmajor and minor defects in beam of these yarns was found to besignificantly reduced in the yarns of the present invention compared tothe standard production.

EXAMPLE 3 8.90 and TE was 31.3. The tenacity of standard production was8.84 and TE was 30.2.

What is claimed is:

l. A heavy denier melt spun polyester filament yarn having a tenacity ofmore than 7.0 grams per denier, a long and short term percent Uster ofless than 1.5, a tensile factor of more than 28, and a breaking strengthstandard deviation of less than 0.20 grams per denier as measured inyarns across a beam.

2. The heavy denier yarn of claim 1 wherein the polyester ispolyethylene terephthalate and the tenacity is greater than 8.0 gramsper denier.

3. The heavy denier polyester yarn of claim 1 wherein the long termpercent Uster is less than 1.0.

4. The heavy denier polyester yarn of claim 1 wherein the denier perfilament is 3 to 20, the total denier is 500 to 5,000, the tenacity is 8to l 1 grams per denier and the tensile factor is more than 30.

1. A heavy denier melt spun polyester filament yarn having a tenacity ofmore than 7.0 grams per denier, a long and short term percent Uster ofless than 1.5, a tensile factor of more than 28, and a breaking strengthstandard deviation of less than 0.20 grams per denier as measured inyarns across a beam.
 1. A HEAVY DENIER MELT SPUN POLYESTER FILAMENT YARNHAVING A TENACITY OF MORE THAN 7.0 GRAMS PER DENIER, A LONG AND SHORTTERM PERCENT USTER OF LESS THAN 1.5 A TENSILE FACTOR OF MORE THAN 28,AND A BREAKING STRENGTH STANDARD DEVIATION OF LESS THAN 0.20 GRAMS PERDENIER AS MEASURED IN YARNS ACROSS A BEAM.
 2. The heavy denier yarn ofclaim 1 whereiN the polyester is polyethylene terephthalate and thetenacity is greater than 8.0 grams per denier.
 3. The heavy denierpolyester yarn of claim 1 wherein the long term percent Uster is lessthan 1.0.
 4. The heavy denier polyester yarn of claim 1 wherein thedenier per filament is 3 to 20, the total denier is 500 to 5,000, thetenacity is 8 to 11 grams per denier and the tensile factor is more than30.